Remote positional control system



vSept. 23,1941. E F. LAZ AR 2,256,787

REMOTE POSITIQNAL CONTROL SYSTEM Filed Jan. 3, 1958 3 Sheets-Sheet lINVENTO tgqwnnn nznn H S ATTORNEY Sept. 23, 1941. E. F. LAZAR 2,256,787

REMOTE POSITIONAL CONTROL SYSTEM Filed Jan. 3, 1938 5 Sheets-Sheet 2INVENTOR wnnp ELnz/m H s A azww is m? MSM Sept. 23, 1941.

I E. F. LAZAR REMOTE POSITIONAL CONTROL SYSTEM 5 Sheets-Sheet 5 FiledJan. 3, 1958 I 1.0 L -L INVENTOR I fan/000E nznn ZBY 7 %[y ig HEJRNEYPatented Sept. 23, 1941 REMOTE POSITIONAL CONTROL SYSTEM Edward F.Lazar, New York, N. Y., assignor to Sperry Gyroscope Company, Inc.,Brooklyn, N ..Y., a corporation of New York Application January 3, 1938,Serial No.183,007

(Cl. 240-12) e 13 Claims.

This invention relates, generally, to positional control systems adaptedfor the positioning of an object such as a searchlight or gun insynchronism with a controlling object or controller, and the inventionhas reference, more particularly, to apparatus especially suitable forlocating and illuminating aircraft at night so that anti-aircraftgunfire may be directed thereon.

The present practice for locating aircraft is to employ a sound locatingdevice such as a binaural sound locator or other non-optical system ofloeating the target blind and to transmit therefrom to a Searchlight theapproximate location of the target, after applying certain corrections,uch as that due to sound lag. Such a system is outlined in the priorPatent. #1976327, dated October 16, 1984, to F. R. House, and is alsodisclosed in Patent #2,003,661, dated June 4, 1935, to P. R. Bassett etal. When using such systems as disclosed in these patents, a continuousseries of datum points or predicted positions is determined irom thedirection of the incoming sound,

with proper corrections applied thereto. It is at a the above listedpatents, are open to certain objections, however, and inaccuracies arisein operation due to the interposition of the control station orcomparator between the sound locator and the controlled Searchlight.Also, in these systems hereofore used, dials are used which are,

operated directly from self-synchronous receivers. This practice isobjectionable because the load thus imposed upon these receivers maytend to introduce errors. Also, in the systems as heretofore generallyconstructed, since there. was no follow-back connection from theSearchlight to the comparator, the searchlight-may fall out ofsynchronism with the sound locator.

The principal object of the present invention is to provide a novelremote positional control system for controlling such objects assearchlights from a sound locator or other control means, in whichsystem the sound locator data is transmitted from the sound-locatordirectly to the search-- light for comparison thereat with the actualposition of the searchiight, the results of this comparisonbeing-employed for operating right-left or zero reader meters orindicatorslocated at the searchlight and at the remote control station,thesaid system enabling a very accurate following of the searchlightfrom the sound locator and eliminating errors of lags present in systemsheretofore used.

Another object of the present invention is to employ A. C. synchronoustransmitters and receivers 01' the signal generator type, the variablemagnitude, reversible phase output being fed into a simple phase shiftdetecting circuit, whereby lag or lead of the searchlight or othercontrolled object is indicated by right or left deflections of anordinary zero reader D. C. voltmeter, suitable step transmitters beingprovided at the controL station for the purpose of operating thesearchlight or other object in accordance with the indications of thezero'reader meter, any error or lag of the step transmitters having noeifect whatever on the accuracy of the system.

Still another object of the present invention is to provide novel meansfor causing the searchlight to search in elevation about the dataposition without causing such searching of the searchlight to beindicated by the control station zero center meter, thereby facilitatingthe following oi the meter indications.

A further object of the present invention is to provide a novel remotepositional control system of the above character, wherein means isprovided for obtaining searching in azimuth, by normal follow-up of thezerocenter meter indications.

Stillanother object of the present invention lies in the provision of anovel remote positional control system of the above character having asingle means or knob for controlling both azimuth and elevation searchof the searchlight.

Other objects and advantages will become apparent from thespecification, taken in connection with the accompanying drawingswherein the invention is embodied in concrete form.

In the drawings.

Fig. 1 is a wiring diagram of the preferred form of the novel remotepositional control system of this invention.

Fig. 2 is an enlarged detailed view, in schematic form, or the controlstation of Fig. 1.

Fig. 3 is a wiring diagram of a somewhat modifled arrangement.

Fig. 4 is a wiring diagram of still another modified arrangement.

Similar characters of reference are used in all of the above figures toindicate corresponding parts.

Referring now to Figs. 1 and 2 of the drawings, the reference numeral Idesignates the sound voltage therein.

locator, which may be of the type shown in the copending application ofFrank R. House, Serial No. 168,704, filed October 13, 1937, now PatentNo. 2,199,404, issued May 7, 1940. The corrected elevation data fromsound locator is transmitted through gearing 2 to an A. C.self-synchronous transmitter 3. The single phase winding of this.transmitter, supplied from A. 0. supply 5 through leads 4, is shown asdriven from the gearing 2, while'the three phase stator is connectedthrough leads 6 to the three phase stator of a self-synchronous receiver1 of the signal generator type, having its rotor of single phaseconnected through gearing 6 to be driven from the searchlight 8 inelevation. As long as the single phase rotor winding of receiver I is atright angles to the field of the three phase stator of this receiver, novoltage is induced in the rotor. Should the receiver rotor be shiftedslightly either clockwise or counter-clockwise from synchronousposition, due to relative movement of the searchlight and sound locatorin elevation, a portion of the field flux of the stator cuts the rotorwinding and produces a signal Clockwise and counter-clockwise shift ofthe receiver rotor causes the signal voltage induced in the rotorwinding to reverse in phase. The variable magnitude, re-

- versible phasereceiver output is fed through sin- Rectifiers l4 and4', preferably of the copper oxide type, are included in leads HIbetween the pairs of resistors I2, I2 and I3, |'3'. A polarizing voltageis supplied to the inner ends of reis centered. The correlation betweendeflections of the meter l6 and the direction of rotation of knob I9 issuch that if the-pointer of meter l6 deflects to the right, the knob isturned counterclockwise, and if the deflection is to the left, the knobis turned clockwise to center the pointer of the meter l6 so as toavoid-180.ambiguity. With I orientation thusly obtained, the knob I9 islocked in position;

sistors l2, l2 and'l3, l3 by leads l5 connected I to one secondary of atransformer l6 supplied from the A. C. source 5. A zero center D. C;voltmeter l6 at the searchlight is connected to leads Ill beyond theresistors l3, l3.

Assuming that the sound locator and searchlight are in elevationalsynchronlsm, the output of the signal generator I is zero, so that therectifiers l4, l4 are caused to rectify the polarizing voltage fromtransformer l6 equally, and hence the zero center voltmeter 16 willindicate zero, that is, this meter will show. zero deflection. Shouldthe searchlight lag the "sound locator, the

voltage output of the receiver adds in phasewith the polarizing voltageacross rectifier l4, for example, and opposes the polarizing voltageacross rectifier |4'. current than H, causing point I'I to becomepositive with respect to point I'l', whereby meter I6 is deflected, forexample, to the left.

Should the searchlight lead the sound locator,

.is connected through gearing 20 to the casing of receiver I for thepurpose of turning the stator thereof. The sound locator I is set atzero elevation, with all corrections removed, and the searchlight 9 isalso set at zero elevation, and the A. C. circuit 5 is energized. Theknob l9, which is preferably located adjacent to the meter I6, is nowturned until the pointer of meter l6 Rectifier i4 passes more rectifyingI Thereafter, non-synchronism between the searchlight and elevation datais indicated by right or left deflection of the pointer of meter l6 andalso of a similar meter 2| located at the control station 22.

The control station 22 may be located at any desired point, taking thesearchlight 9 as a center. Thus, for example, the searchlight may belocated at, for example, 900 feet from the sound locator, and thecontrol station 22 may be located, for example, at 700 feet from thesearchlight 9 at any angle. These figures are given by way of example,however, and it is to be understood that they may be increased toseveral thousand feet without any adverse eflect upon the accuracy ofthe system due to its inherent sensitivity and accuracy.

One of the leads I'll is connected directly by a lead 23 to theright-left meter 2|, at the. control station, whereas the other lead I0is connected through a lead 23' extending to the midtapo'f apotentiometer 24, the slider 44 of which is connected by a lead 25 tothe meter 2|. It will be apparent that with the slider of potentiometer24 at its central position, the meter 2| will be directly connectedacross the output of the elevation phase detector II, as is true ofmeter l6. Hence, non-synchronism between the searchlight and elevationdata is indicated by left or right deflection of meter 2|. The elevationfollow-up handwheel 26 at the control station is connected throughgearing 21 to drive the step-by-step transmitter 28 which synchronouslycontrols the elevation step-by-step motor 29 which is connected throughgearing 30 for driving the searchlight about its elevation axis.

The correlation between the deflections of meter 2| and the rotation ofhandwheel 26 is similar to that existing between meter l6 and knob l9-atthe searchlight. Hence, in order to maintain synchronism between thesearchlight and the moving elevation data, it is only necessary to turnelevation follow-up handwheel 26 so as to steer or move the pointer ofmeter 2| to zero.

This action takes place continuously while following the sound locatordata, and should it be necessary to search for the target, the observerat the control station is provided; with a knob or handle 3| (see Fig.2) which, when depressed, servesto close a switch blade 32Lupon astationary contact 33, thereby completing a circuit for a search motor34 from D. C. supply leads 35. The field 36 ofmotor 34 is permanentlycon-- nected across leads and a variable resistor3l is connected in thearmature circuit of motor 34 for varying the speed thereof at will.Motor 34 drives-a crank disc 31 whose eifective radius is adjustable bymoving crank pin 38'. This crank disc operates through link 39 tooscillate a sector plate 40 which, in turn, acts through suitablegearing for turning one arm of a differential 4| having another armthereof driven from the elevation control handwheel 26. Thus, bydepressing handle 3|, motor 34 is caused to operate to efiect anoscillation of sector plate 46 which, in turn, acts to superimpose uponthe movements imparted to the elevation step-bystep transmitter 23 fromhandwheel 26 an oscillatory motion which causes the searchlight 3 tooscillate in elevation at a speed and amplitude determined by theadjustment of the crank pin 38' and that of resistor 31 in the circuitof motor 34. The elevation potentiometer 24 has one side thereofconnected through leads 42, including a resistor 45 to one side of theD. C. supply 35, whereas the other side of potentiometer 24 is connectedthrough a lead 43 including azimuth potentiometer 24' to the other sideof supply 35. Hence, displacement of the slider 44 of potentiometer 24from its central position causes'a D. C.

voltage to be inserted in series with the output of the elevation phasedetector thus affecting the reading of meter 2|. The slider 44 isshifted by a rod 46 so as to turn with the sector plate 40. The polarityof the D. C. supply for potentiometer 24 and the angular movement of theslider are so arranged that the voltage inserted in series with meter 2|is equal and opposite at every point to the output of the phase shiftdetector due switch knob 3| under action of spring 66 serving to causeswitch plate 32 to engage stationary contact 33', thereby shorting thearmature of motor 34. The observer at the control station then keeps thetarget in the beam by use of the observer's handwheel 41, the follow-upoperator relinquishing the elevation control follow-up handwheel 23.

When tracking ceases, the observer rotates knob 33 on the shaft of motor34 until the oscillation indicator 43 operated from sector 40 indicatesthat the slider 44 is in'its central position, thereby eliminating anyoffset remaining from the previous operation.

The equipment used for providing for azimuth operation of thesearchlight is similar to that used for elevation operation thereof, andparts of the azimuth operation equipment that are similar to parts ofthe elevation equipment are similarly numbered, though provided with thesubscript I.

Orientation or initial synchronization in azimuth is accomplished bypointing the sound 1 cator together with the searchlight in azimuth at acommon distant object, such as the sun or a star, and then adjusting bymeans of knob I31 the pointer of meter I61 to its zero center position,and then locking knob I91. While the azimuth data is being followed inthe usual way, the slider 44' is in its central position onpotentiometer 24', and meter 2|1 is directly across the output of phasedetector 1. Should the observer desire to sweep the searchlight beam tothe right or left of the azimuth data, it is mere- 1y necessary for himto slowly turn the knob or handle 3|, correspondingly shifting theslider 44' wheel 231, causes the desired searchlight azimuth shift fromthe data. So long as knob 3| is oscillated'or turned at a rate notexceeding the capability of the follow-up, operator to center the zeroreader, the searchlight oscillates in azimuth about the data insynchronism with the rotary movement of knob 3|.

In practicalfield use, it sometimes happens, owing to meteorological orother conditions, that the sound locator data consistently lags or leadsthe target in azimuth. In such case, the azimuth offset knob 3| providesa convenient means of inserting a compensating correction so that thechances of pick-up without azimuth search are enhanced. Should, for anyreason, the control station 22 become inoperative, the searchlight 3 maybe disconnected from the step motors 29 and 291 and thereafter the samemanually operated to follow the data by use of the zero readers I3 andI61 located at the searchlight.

The accuracy obtainable when using the system of this invention isconsiderably greater'than that obtainable with the ordinary systemsheretofore used. The electrical field shift-of the receiver signalgenerator is utilized directly for operating the meters I3, I61, 2| and2h to thereby show any displacement of the telescope II from data. Thistelescope is mounted on top of the control station 22 and is usuallyconstructed as a binocular. It rotates in azimuth with the housing 1 I,which is controlled from the handwheel 26' or 41' by means of a geartrain. A worm and worm gear 13 moves the telescope in elevation and iscontrolled from handwheels 26 or 41 by means of bevel gears I4, shaft 15and bevel gears IS. The errors in the ordinary data systems heretoforeused arise from the fact that the electrical field shift in thereceivers is required to do mechanical work in overcoming friction inpositioning the rotors to which the indition. In an emergency it is alsopossible and convenient when using' the present system to 'have thepersonnel at the Searchlight follow the sound locator by manual controlby using the zero readers, 1. e. meters l6 and I61 at thesearchlight.

An important feature of the invention lies in the fact that since thereceiver has to do no work, such as turning its rotor and dial, thecurrent in the leads '6, 61 and lb very small, permitting the use ofsmall cables. Likewise, the separation between sound locator andsearchlight may be increased to several thousand feet without adverseeffect upon the accuracy.

Furthermore, while the zero reader type of control apparatus, asinvolved in this invention, retains all the advantages of the comparatorcontroller repeat back system, nevertheless the same offers additionalimprovements in accuracy and in greater simplicity in apparatus, and fargreater flexibility in location of the sound locator, searchlight andcontrol station. Preferably, the zero reader meters I6, I61, 2| and 2hare non-linear with misalignment of the sound locator and searchlight,the deflection being large for small lag or lead for enabling closefollowing, the deflection increasing more slowly for largermisalignments.

If desired, the phase detectors II and H1 may be located at the controlstation 22- instead of at the searchlight 3. In this case, thepotentiometers 24 and 24' at thecontrol station may vries the otherwinding 52.

' is located at the searchlight.

of phase detector II and I31 and |3'1 of phase detector 1. In this casethe taps 49 of phase detector II and 49' of phase detector 1 areadjustable as sliders over the potentiometer. With the sliders in thepositions corresponding to the showing of Fig. 1, the phase detectorbridge circuits are symmetrical and deflections of the zero readers l6,2| and I61, 2|1 are correct indications of the searchlight positionrelative to the data. Should either slider be displaced, however, fromthis position, the corresponding bridge circuit is renderedunsymmetrical and furnishes an output voltage to the zero readers forzero input from receiver 1 or 11, as the case may be, and the polarityof this voltage reverses as the slider is moved to the left or right ofthis mid Position. The slider of the elevation potentiometerelectrically connected between leads I would be mechanically connectedfor oscillation by the oscillating sector plate I, and the slider of theazimuth potentiometer would be connected for rotation by knob 3|,thereby producing compensation for elevation search and providing forazimuth search or ofiset.

In Fig. 3, a somewhat modified form of the invention is illustrated. Inthis figure, for the sake of simplicity, only the apparatus forobtaining elevation control of the searchlight 9 is figures aresimilarly numbered. In this form of the invention, the oscillation orsearch of the searchlight is accomplished through use of an auxiliarymotor 55 that operates through worm and wheel gearing 51 and link 58 andsector 59,

pivoted at 60, to turn one arm of a difl'erential control station may beused for controlling the auxiliary motor 56, a

In order to remove any oscillation ofiset remaining after an operation,the switch 55 at the control station is provided, which, when closed,

causes the motor to run until a stationary con- 1 tact 62' is disengagedby a movable blade contact 63, carrying a roller 64 movable over thesector plate 59. At the position of zero search amplitude, the roller 64enters a notch in the sector plate 59, thereby opening the circuit ofmotor 58. Difierential gearing 65 is shown in Fig. 4 operated from thesearchlight 9 and connected to the single phase rotor of the receiver 1for shown, the azimuth apparatus being similar to that illustrated inFig. 2. Parts of this figure which are similar to corresponding parts ofFigs. 1 and 2 are similarly numbered.

In this form of the invention, the sound locator data supplied fromtransmitter 3 is passed through differential data units consisting ofinductively related three phase windings 5| and 52 in the remote controlstation 22'. One of these windings is usually a stator. winding 5| in ahousing providing bearings for a rotor which carcommonly known in theart as electrical differentials". As used in Fig. 3, the diiferentialserves to add to the positional signal in winding 5| another positionalsignal created by the mechanical rotation of rotor windings 52,delivering to winding 1 a positional signal equal tothe sum of the twofirst named signals. The receiver The elevation difierential unit rotor52 is connected through gearing 53 to a sector plate 40' similartosector plate 40 of Fig. 2 of the drawings. As in Fig.2, sector plate 40'is oscillated by crank disk 31 .driven from motor 34, and, in turn,plate 40' acts through suitable gearing to turn one arm of thedifferential 4| having another arm thereof driven from the elevationcontrol handwheel 26, thereby superimposing upon the movements impartedto the elevation step-by-step transmitter 28 from handwheel 26 anoscillatory motion which causes searchlight 9 to oscillate in elevation.Sector plate 4|! serves to oscillate the unit 52 and thereby subtractfrom and add to the data, potentials corresponding and opposite'to thoseput out by the phase shift detector due to the excursion or searching ofthe searchlight, whereby such searching causes'no movement of thpointers of meters I6 and 2|. Similarly, the azimuth differential unit,not shown in Fig. 3, is geared to the knob 3| of Fig. 2 to add to thedata the azimuth search desired. Further description of this figurewould appear to be unnecessary.

Inthe form of the invention shown in Fig. 4, parts that are similar toparts of the preceding Such devices are the purpose of removing orerasing the oscilla-- tory movements from the receiver so that thesearch does not affect the zero reader indication of meters I6 and 2|,thereby facilitating the operation of the elevation follow-up handwheel26 at the control station. The center arm of this diiierential is meshedwith the center arm of differential 6|, thereby causing oscillationofthe rotor of receiver 1. At the sam time, an equal and oppositeoscillation is introduced through the third arm, geared to thesearchlight, so that both oscillations cancel out.

Only the elevation control apparatus is shown in this figure, as in Fig.3, the azimuth control apparatus being similar to the elevation control,and hence would appearnot to require illustration. The azimuthoscillation motor, not shown, is preferably controlled by a reversingswitch at the control station, so that the searchlight may be swungslowly to the right or left of the data desired. An azimuth centeringdevice similar to that employed in the elevation apparatus may be used.

It will be apparent that instead of using a sound locator in connectionwith the system of this invention, other non-optical locating means,such as infra-red detectors, or radio wave detectors, may be used, ifdesired, all within the scope of the appended claims.

As many changes couldbe made in the above construction and manyapparently widely different embodiments of the invention could be madewithout departing from the scopethereof, it is intended that all mattercontained in the above description or shown in the accompanying drawingsshall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In, a remote positional control system, a sound locator, a remotesearchlight arranged to be controlled in accordance with datatransmitted from said sound locator, transmission means for conveyingthe data directly from said sound locator to said searchlight forcomparison from, means for converting the results of said compared datainto a reversible direct current voltage, a right-left meter at saidcontrol station fed from said voltage, and a distant electrical controlsystem connecting said control station and said searchlight foroperating the latter in accordance with said meter indications.

2.-In a remote positional control system, a sound locator, a remotesearchlight arranged to be controlled in accordance with datatransmitted from said sound locator, transmission means for conveyingthe data directly from said sound locator to said searchlight forcomparison thereat with th actual position of said searchlight, acontrol station located'atany desired position about said Searchlightand remote therefrom, means for converting the results of said compareddata into a reversible direct current voltage, a right-left meter atsaid control station fed from said voltage, a distant electrical controlsystem connecting said control station and and electrically connected tosaid transmitter, a

searchlight, and means for superimposing an. oscillatory movement on therotation of said.

remote control station, a phase shift detecting circuit fed from saidreceiver, a step by step transmitter at said control station andelectrically connected to a step by step receiver at said controlledobject for moving the latter, a zero center "meter at said controlstation fed from said phase shift detecting network for use in operatingsaid step by step transmitter, and manually controlled means forsuperimposing external potentials of changing polarity to said meter,whereby manual operation of said step by step transmitter to maintainsaid meter centered automatically produces search movement of saidcontrolled object.

6. In a remote positional control system, a target position locator, acontrolled object, a

self-synchronous transmission system intercon necting said locator andcontrolled object, a remote control station, a phase shift detectingcircuit fed from the receiver of said system, a step by steptransmission system extending between said control station and saidcontrolled object for moving the latter, a right-left meter at saidcontrol station fed from said phase shift detectmitted from said soundlocator, transmission from, means for converting the results of said. I

compared data into reversible direct current potentials, a right-leftmeter at said last named control station fed from said means, a distantelectrical control system connecting said control station and saidsearchlight for operating the latter in accordance with said meterindications, said control system having a rotatable transmitter at saidcontrol station and a receiver at said searchlight, means for adding anextraneous oscillatory movement to the rotation of said transmitter toefiect searching of said Searchlight about its datum position, and meansoperated from said last named means and connected to said right-leftmeter for preventing said meter from indicating said oscillations.

4. In a} remote positional control system, a target position locator, acontrolled object, a self-synchronous transmission system having atransmitter and receiver electrically connected for interconnecting saidlocator and controlled object, a remote control station, a phase shiftdetecting circuit fed from the receiver of said system, a step by steptransmission system having a transmitter and a receiver electricallyconnected for interconnection between said control station and saidcontrolled object for moving the latter, wright-left meter at saidcontrol station fed from said phase shift detecting circuit for use inoperating said step by step transmission system, and means forautomatically adding a search oscillation to the rotation of said stepby step transmitter to effect searching of said controlled object, andmeans operated by said oscillating means to synchronously'change theconstants of said phase shift detecting circuit, whereby the eflect ofthe searching of said coning circuit for use-in operating said step bystep transmitter, and means for superimposing a search oscillation onsaid step by step transmitter to effect searching of said controlledobject, said means also serving to synchronously apply externalpotentials of changing polarity and value to said meter, whereby thepotentials produced by the searching motion of said controlled objectare counterbalanced in their effect on said meter.

7. In a remote positional control system, a target position locator, acontrolled object, a selfsynchronous transmission system interconnectingsaid locator and controlled object, a control station, a two-partelectrical difierential at said station and included 'insaid system, astep by step transmission system extending between said control station'andsaid controlled object for moving the latter, a phase shiftdetecting network fed from the receiver of said self-synchronoustransmission system, a right-left meter at said control station fed fromsaid network. foruse in operating said step by step transmitter,

and means for turning one part of said electrical a right-left meter atsaid control station opermeter indication is rendered independent ofsaid oscillation.

9. In a remote control system for positioning a controlled object inaccordance with positional data transmitted from a reference object, acontrolled object, a reference object, a self-synchronous transmittersupplying an electrical signal in accordance with the position of saidreference object, a self-synchronous receiver comprising a stator and arotor receiving said signal, said rotor being mechanically connected tosaid controlled object for generating an alternating voltage variable inmagnitude in accordance with the disagreement of the position of saidcontrolled object and the positional data supplied by said signal andreversing in phase as said controlled object passes through the positioncorresponding to said data, a phase sensitive circuit receiving thevoltage of said'rotor,

and supplying a D. C. voltage having a magnitude and polaritycorresponding to the magnitude and phase of said rotor voltage, a zerocenter meter located at a control station remote from said controlledobject and connected to said circuit for indicating the magnitude andsense of the deviation of said controlled object from said position ofcorrespondence, remote control means including a step-by-steptransmission system for means and searchlight, a control station, atwopart electrical differential at said station and included in saidsystem, a step by step transmita ter system extending between saidcontrol station and said searchlight for moving the latter,

means for automatically adding an oscillatory movementto the movement ofsaid step by step transmitter for producing searching of saidSearchlight and for oscillating one part of said differential tocompensate for the eflect of such searching of said searchlight on saidself-synchroncus transmission system.

1. In a three-station sound locator-searchlight system, the combinationwith-a sound locator, searchlight and remotely located control stationhaving a sight thereat, A. C. self-synchronous transmitters at saidsound locator and actuated by rotation in azimuth and elevation thereof,signal generators at said searchlight activated by said transmittersupon disagreement in angular position of said sound locator and,searchlight in azimuth and elevation, respectively, a pair ofzero-reader indicators at said control station controlled respectivelyfrom said signal generators, and manually operable azimuth and elevationtransmitters at said control station for synchronously operating saidsearchlight in azimuth and elevation either in accordance with saidindicators or said sight at will.

12. In a searchlight-sound locator system, the combination with asearchlight and a remote sound locator, means for generating a, primaryelectrical signal proportional to the positional disagreement or saidsearchlight and sound locator, an indicator operated by said signalwhereby said Searchlight and locator are maintained directed at the sametarget, additional means for giving said Searchlight periodic limitedsearching movement, a second generating means for generating a secondarysignal proportional to said searching movement, and means forsuperimposing said secondary signal on said primary signal, whereby saidindicator is rendered insensitive to the aforesaid searching movementsof said Searchlight.

13. In a three-station sound locator-searchlight-remote control stationsystem capable of operation without reference to the control station,the combination of a sound locator, a searchlight, AHC. self-synchronoustransmitters, at said sound locator, actuated by rotation in azimuth andelevation thereof, signal generators, at said searchlight, actuated bysaid transmitters upon disagreement in angular position of said soundlocator and Searchlight in azimuth and elevation, respectively, a pairof zero-reader indicators, at said searchlight, controlled respectivelyfrom said signal generators, and manually controlled means, at saidsearchlight, by which the sear'chlight is rotatable in azimuth andelevation in accordance with the reading on said indicators.

EDWARD F. LAZAR.

